Radio Frequency (RF) shielding is required on certain semiconductor devices and modules (hereinafter semiconductor device) in order to minimize Electro-Magnetic Interference (EMI) radiation from the semiconductor device. RF shielding is further required to prevent RF radiation from external sources from interfering with operation of the semiconductor device.
RF shielding for a microphone semiconductor device creates a particular issue. In microphone devices, a sound opening is formed in a substrate to allow the microphone to pick-up and receive sound waves. The sound opening must remain uncovered so that the microphone may properly receive the sound waves. However, the sound opening allows noise and other outside conditions to enter the device and interfere with the proper operation of different components of the device.
RF shielding for a microphone semiconductor device is generally accomplished in one of three ways. A first method is to attach a metal can over the component after the component is attached to the motherboard. An alternative to the shield attached method described above is an embedded RF shield. In an embedded shield, the metal RF shield is directly attached to the semiconductor package substrate by means of solder or a conductive adhesive. The shield may be fully embedded within the mold compound of the finished package or can be exposed after assembly. The third method is the conventional conformal shield. Conformal shielding is the latest technology to support integrated circuit (IC) devices and System in a Package (SiP) modules shielding. The conformal shielding creates a metallic coating, which is attached to ground metal in the substrate to provide a full shielding result. Presently, the conductive coating is applied to non-conductive surfaces, i.e., mold compound, substrate, etc.
All of the above methods provide an RF shield over a top surface of the microphone device. A ground guard is generally formed around the outer perimeter of the substrate. The RF shield is generally placed on a top surface of a substrate of the microphone device and attached to the grounding plane to provide the RF shielding. However, the sound opening on a bottom surface of the microphone device needs to remain uncovered so that the microphone may properly receive the sound waves. Thus, the sound opening allows noise and other outside conditions to interfere with the proper operation of the microphone device.
Therefore, a need existed to provide a system and method to overcome the above problem. The system and method would provide for RF shielding for a MEMS microphone package.